The objective of this Phase I application is to develop a serum-based biomarker for acute neuronal degeneration. This test is needed to assess several clinical indications including traumatic brain injury (TBI), as well as, a surrogate endpoint for assessing the efficacy of neuroprotective agents. We have developed a sandwich ELISA for quantifying a neuronally localized protein, MAP-tau, that is released from damaged neurons. Employing this MAP-tau ELISA, we have shown that MAP-tau cerebrospinal fluid (CSF) levels are elevate 10,000 fold in TBI patients. In preliminary studies, we demonstrate that serum MAP-tau levels are elevated 40 fold in TBI patients compared to controls. The proposed studies will assess the clinical feasibility of measuring neuronal damage in TBI patients by quantifying serum MAP- tau levels. The Specific Aims are: Specific Aim 1: Determine if serum MAP-tau levels are elevated in TBI patients (N=30) compared to neurologic controls (N=30) and non-neurologic controls (N=30). Specific Aim 2: Determine the time course of elevated serum MAP-tau levels in TBl patients (N=15). Specific Aim 3: Determine if the elevation of serum MAP-tau is associated with an injury-related elevation in CSF MAP-tau that diffuses into blood via a compromised blood brain barrier. PROPOSED COMMERCIAL APPLICATIONS: The objective of this Phase I application is to develop a serum-based biomarker for acute neuronal degeneration. This test is needed to assess several clinical indications including traumatic brain injury (TBl), as well as, a surrogate endpoint for assessing the efficacy of neuroprotective agents.